It is often desirable to use sport goggles, dive masks and other highly portable transparent eye-protecting shields in environments involving conditions which contribute to condensation build-up on the eye shield and where even momentary impairment of vision by fogging would be problematic. When the temperature of such an eye shield has dropped below a dew-point temperature, i.e., the atmospheric temperature below which water droplets begin to condense and dew can form, fogging has occurred.
A common characteristic of such portable eye-protecting shields is the fact that they are lightweight enough to be worn on a user's head and are positioned relatively closely to a user's face such that the user's breath and body heat exacerbates fogging conditions. Examples of fog-prone sport goggles intended for use during winter activities have included goggles for downhill skiing, cross-country skiing, snowboarding, snowmobiling, sledding, tubing, ice climbing and the like, and are widely known and widely utilized by sports enthusiasts and others whose duties or activities require them to be outside in snowy and other inclement cold-weather conditions. Examples of fog-prone dive masks have included eye and nose masks independent of a breathing apparatus as well as full-face masks in which the breathing apparatus is integrated into the mask. Examples of fog-prone eye-protecting shields have included a face shield that a doctor or dentist would wear to prevent pathogens from getting into the user's mouth or eyes, or a transparent face shield portion of a motorcycle or snow-mobile helmet. Fogging that impairs vision is a common problem with such goggles, dive masks and eye-protecting shields.
There have been various conductive apparatus devised for preventing condensation build-up on eye-shields for eye-protecting shields, and while a rectangular eye shield with a thin-film heater may have been evenly heated across the eye-shield, but none have taught a method for employing a thin-film heating system in an eye shield that enables even heating of the eye shield, or alternatively customized heating of the eye shield according to a lens heating profile, according to the configuration and application of the thin-film heating material to the eye shield. The purpose of these conductive apparatus has been simply to provide an eye shield that may be maintained free of condensation so that the user would be able to enjoy unobstructed vision during viewing activities, and as such they have been subject to problems of creating hot spots on irregular-shaped lenses and have not provided for customizable heating of lens. Prior sports goggles with electronic systems have been primarily used in environments requiring a high degree of portability, that is, where a power source for powering the electronics for the device has been advantageously carried on a strap for the goggle or on the goggle itself as shown and described in co-pending U.S. patent application Ser. No. 13/519,150, by McCulloch et al., for Goggle with Easily Interchangeable Lens that is Adaptable for Heating to Prevent Fogging.
Some examples of disclosures providing for heating of goggle lenses include the following: U.S. Pat. No. 4,868,929, to Curcio, for Electrically Heated Ski Goggles, comprises an eye shield with embedded resistive wires operatively connected via a switching device to an external power source pack adapted to produce heating of the eye shield for anti-fog purposes. The Curcio disclosure does not teach even heating of a lens, or alternatively customized heating of a lens, by employing a certain configuration of thin-film heating material on the lens.
US Patent Application No. 2009/0151057A1 to Lebel et al., for Reversible Strap-Mounting Clips for Goggles, and U.S. Pat. No. 7,648,234 to Welchel et al., for Eyewear with Heating Elements, disclose use of thin-film heating elements used for heating an eye shield with a push-button switch for turning on power from a battery carried on an eyewear band or eyewear arm. Neither Lebel et al. nor Welchel et al. teach even heating of an irregular-shaped lens, or alternatively customized heating of the lens, by employing a certain configuration of thin-film heating material on the lens.
U.S. Pat. No. 5,351,339 to Reuber et al., for Double Lens Electric Shield, recognizes the problem of un-even heating where an electroconductive film is deposited on an irregular-shaped visor lens and proposes a specific bus bar configuration (electrodes 50 and 60) that addresses the problem of making the distance between electrodes substantially the same for fairly uniform flow of electrical current across the electroconductive film. However, Reuber et al. does not disclose even heating of a lens, or alternatively customized heating of the lens in accordance with a heating profile, by employing a certain configuration of thin-filmed heating material on the lens. Further, the eye shield of Reuber et al. was more uniform than that of a conventional goggle having a cutout portion adapted to fit over the bridge of a user's nose. Accordingly, the configuration of the electrode bus bars of Reuber et al. would not suffice for a more conventional goggle lens configuration.
Thus, a problem with sport goggles which have employed electrical heating is that of uneven heating over the entire surface of an irregular-shaped eye shield. Goggles and dive masks, and their eye-shields, are manufactured with an irregular shape required to maintain a position close to the face of the wearer and allowing cutouts for the nose and extended edges for peripheral vision. While various general attempts to evenly heat an eye shield across its entire surface have been made with serpentine wires included on, or within, eye shield lenses, as for example in published US Patent Application No. 2008/0290081A1 to Biddel for Anti-Fogging Device and Anti-Fogging Viewing Member, and U.S. Pat. No. 4,638,728 to Elenewski for Visor Defroster, even heating of an irregular-shaped eye shield, or customized heating of such an eye shield, with a thin film heater has not been taught in the prior art.
Lebel et al. would be susceptible to hot spots, and using such devices in limited battery-powered applications has unduly discharged the battery. The reason for the hot spots has been because the electrical resistivity between the electrical connections across the resistive elements on the eye shield has been greater or lesser at different locations on the eye shield such that the amount of electrical current consumed in the areas with less distance between terminal connections is greater and the amount of electrical current consumed in areas with greater distance between the terminal connections is less. For example, where the terminals are on either side of the lens in a resistive wiring application, there have been problems with evenly heating the lens since the distance the wire has had to travel from one terminal to the other has been greater for those wires traveling over the bridge of the nose and down under the eyes than other wires that travel the shorter distance across a central portion of the lens. To overcome fogging conditions enough power must be applied to overcome the fog in the areas with the greatest distance between the terminal connection points, causing the smaller areas to overheat, which in turn wastes power. Thus, the problem has resulted in limited usefulness of heating of goggle eye-shields. Because of the irregular shape of eye shields, these problems exist whether one is considering resistive-wire applications or resistive-film applications.
Still another problem associated particularly with goggles and dive masks is the amount of space provided between the eye shield portion of the device and the user's face. Where insufficient space has been provided, the wearing of corrective lens eye glasses within the goggle or mask has been prohibited. Further, where excess distance has been provided between the shield portion of the device and the user's eyes, the ability to incorporate corrective lenses into the goggle or mask eye shield itself has been prohibited. Increased distance between the user's eyes and the eye shield has improved anti-fogging capability in typical air-flow dependent anti-fog goggles, however, locating the eye shield at such a great distance from the user's eyes to facilitate anti-fogging has made corrective goggle lenses less effective for correcting vision, because excessive lens thickness would thus be required to accommodate the higher degree of curvature necessary in the lens to make the necessary vision correction. Thus, what has been long needed in the corrective lens goggle, or dive mask, art is a technology that would both permit a corrective eye shield lens to be sufficiently close to the user's eyes to function properly from a vision correction perspective, but which is also capable of effective fog prevention. Thus, there has developed a need to balance regions of eye shields to enable even heating of eye shields across the entire eye-shield surface without excessive use of power or hot spots and without excessive space between the user's eyes and the eye shield itself for vision correction lens purposes.